<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Javascript Study</title>
  </head>
  <body>
    <script lang="text/Javascript">


      function fun(n,o) {
              console.log(o)
              return {
                  fun:function(m){
                      return fun(m,n);
                  }
              };
          }
          var a = fun(0);  a.fun(1);  a.fun(2);  a.fun(3);//undefined,?,?,?
          var b = fun(0).fun(1).fun(2).fun(3);//undefined,?,?,?
          var c = fun(0).fun(1);  c.fun(2);  c.fun(3);//undefined,?,?,?
    </script>
  </body>
</html>
